Automobile seats (i.e., seats and backrests) have heretofore, for the most part, been made from fabric-covered foam cushion material. The furniture industry has found that fiber cushions are more durable than foam, more breathable than foam, less costly than foam, more readily recyclable than foam, and do not emit gases during processing. Such cushions would offer similar advantages to automobile manufacturers desirous of reducing costs and increasing the recyclable content of its vehicles.
It is known to make fiber-filled cushions from mixtures of high melting point and low melting point fibers by heating the mixture in an oven so as to soften and unite the low melting fibers (hereafter bonding fibers) with the high melting fibers (hereafter matrix fibers) at their points of intersection, anti then cooling the mixture sufficiently to bond the bonding fibers to the matrix fibers. Typically, the bonding fibers comprise only about 25% to about 30% by volume of the fiber mix, but more or less may be used. It is difficult to achieve uniform of the fibers in an oven in a short processing cycle time and this difficulty increases as the thickness of the cushions increases. Often the fibers at the center of the cushion do not fuse as well as those closer to the surface of the cushion. Attempts to accelerate heating in the center of the mixture by increasing the oven temperature only serves to overheat the fibers closer to the surface. Such a process is not only difficult to control but results in a nonuniform product. On the other hand, using lower oven temperatures, and consequently longer heating times adds to the cycle time and cost of the process.
It is a principle object of the present invention to provide a unique, readily controllable process and apparatus for quickly and substantially uniformly heating a mixture of high and low melting point fibers to make a seat cushion, and particularly a process/apparatus which is readily adaptable to producing cushions with distinct zones having different physical properties (e.g., softness). This and other objects and advantages of the present invention will become more readily apparent from the detailed description thereof which follows.